1. Field of the Invention
The present invention relates in general to a touch panel interface device, and more particularly to a data input/output control unit for the touch panel interface device in which a system control part is designed with a digital logic circuit for use in a portable system, and a present mode is changed to a suspend mode after the lapse of a predetermined time period from the moment that no data is applied to a touch panel, to turn off supply power to the touch panel and stop a system operation, so that power consumption can be minimized and a battery can be lengthened in life, in particular in small, portable equipments such as a personal digitizer assistant (referred to hereinafter as PDA) and the like.
2. Description of the Prior Art
Referring to FIG. 1, there is shown a schematic block diagram of a conventional touch panel interface device. As shown in this drawing, the conventional touch panel interface device comprises a touch panel 1 for sensing coordinates of a point touched by a user's pen and generating an analog signal in accordance with the sensed result, a read only memory (referred to hereinafter as ROM) 5 for storing a control program for controlling a system operation, a micro controller 4 for executing the control program stored in the ROM 5 to control the system operation, an analog/digital (referred to hereinafter as A/D) converter 2 for converting the analog signal from the touch panel 1 into digital data in response to a control signal CS10 from the micro controller 4 and outputting the converted digital data to the micro controller 4, a switch 3 for turning on/off supply power to the touch panel 1 in response to a control signal CS20 from the micro controller 4, and a serial communication circuit 6 for performing a serial communication with other systems in an RS-232 manner in response to a control signal CS30 from the micro controller 4.
The operation of the conventional touch panel interface device with the above-mentioned construction will hereinafter be described with reference to FIG. 1.
Upon power-on, the micro controller 4 outputs the control signal CS10 to the A/D converter 2 according to the control program stored in the ROM 5 to sense input data.
If no data is sensed, the micro controller 4 outputs the control signal CS20 to the switch 3 to turn off the supply power to the touch panel 1.
In the case where data is applied to the touch panel 1 by the user's pen, the corresponding coordinates are sensed by the touch panel 1. Then, the touch panel 1 outputs the analog signal corresponding to the sensed coordinates to the A/D converter 2, which converts the analog signal into the digital data in response to the control signal CS10 from the micro controller 4 and outputs the converted digital data to the micro controller 4. Then, the micro controller 4 stores the digital data from the A/D converter 2 into a random access memory (referred to hereinafter as RAM), not shown.
The micro controller 4 transfers the data stored in the RAM and the control signal CS30 to the serial communication circuit 6 to perform data transmission and reception with other systems. The serial communication circuit 6 may include, for example, a universal asynchronous receiver/transmitter (UART). Then, the serial communication circuit 6 performs the serial communication with other systems in the RS-232 manner.
However, the above-mentioned conventional touch panel interface device has a disadvantage in that an internal structure cannot be known because the micro controller and the ROM are provided on a single application/specific integrated circuit (referred to hereinafter as ASIC) chip in a manufacturing process. For this reason, it is difficult to perform precision control for system implementation. Further, power consumption is increased because the power is always supplied to the other blocks and the micro controller scans the data input continuously by means of the A/D converter. This results in a reduction in life of a battery, particularly in small, portable equipments such as a PDA and the like.